Phil Plait

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Should you be worried about an asteroid impact? Live Conversation with Phil Plait - Join now!

This Conversation will open on December 1st, 1 pm EST.

Asteroids are the solar system's leftovers: chunks of rock and metal ranging in size from too small to see to hundreds of kilometers across. They pose a great threat to life on Earth - just ask a dinosaur, which you can't, because an asteroid wiped them out - but they're also a great opportunity for science and possibly even for our economy. What do we know about them, what don't we know, what do we wish we knew? Now you can find out: Dr. Philip Plait, astronomer and science evangelizer, will answer your asteroidal questions live on December 1 from 1-2 pm. EST.

Watch his talk: " How to defend Earth from asteroids"

Closing Statement from Phil Plait

First, thank you to the folks at TED and of course to everyone who came to ask questions! That was exhausting, but fun. I don't think I've ever typed faster in my life. :)

If there's one thing I want you to take away from this topic, it's this: the threat from comets and asteroids is small - very small; after all, we're still here! - but real. If we wait long enough (decades? centuries?) then some rock big enough to do damage will come along. We have to take this threat seriously, and the good news is lots of people are.

We are scanning the sky looking for these potential impactors, we have more telescopes coming online in the next few years to make the search deeper and more efficient, and there are lots of ideas on what to do should we see such a rock headed our way. Odds are we'll have a few years notice for any big threats. My hope is that by talking about this, by spreading the word and getting more folks interested in it, we'll have an even better chance of fighting back if and when that time comes.

Thanks again!

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    Dec 1 2011: Hi everyone! Welcome to my TED Q&A live comment chat. I'm honored and happy to have been invited to do this with all of you!

    Got any questions about asteroid impacts, terrible movies about asteroid impacts, what people are doing about asteroid impacts, or anything else space or astronomy-related?
  • Dec 1 2011: There has been ideas of putting a transmitter on Apophis in order to most accurately track it' s orbit and definitively determine it's threat to us. What do you think such a mission would cost and would people support it? What about a global effort?
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      Dec 1 2011: I love this idea, actually! We'd learn a lot about asteroids, and it would teach us how better to track them. A tracking device wouldn't be the only goal of such a mission, of course; we'd also be able to map out the surface, learn about the mineralogy of it, and many other interesting and important scientific questions. So the cost would be about the same as any other asteroid mission - hundreds of millions of dollars - but in real terms that's a small amount compared to, say, what Americans spend on cigarettes or pet food or cosmetics every year. And in this case, we might save the world!
  • Dec 1 2011: Hi Phil,

    If we happened to wake up in the morning to discover an asteroid of (suitably scary size) on a collision course with Earth how prepared would we be technologically to correct its course and how much warning would we require to put a plan into place (given unlimited money and government cooperation?
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      Dec 1 2011: In reality, the longer the better! But we currently do NOT have a rocket and probe ready to go to prevent such a thing. It would probably take a few years to put a mission together, and then a few more at least for it to properly move the rock. The good news is, statistically speaking, we have time.It may be years before such a threat turns up. But I'd like for us to be ready when it occurs.
      • Dec 1 2011: Thanks for the answer Phil. Keep up the good work on making people aware :)
  • Dec 1 2011: Hey Phil,
    Loving the blog! With the asteroid 2004 MN4 that has a chance of crossing into Earth's path in 2029, what do you feel is the best preventative measures we can take? Or more specifically, would it be possible to shift its path with say an extremely large object that would affect its gravity?
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      Dec 1 2011: 2004 MN4, better known as Apophis, has a one in a million chance of hitting us, so I'm not worried about it. I'm more worried about slipping in the bathtub! (seriously) But the best thing we can do is treat it as a test case. We should put a mission together to visit it so we can learn how better to rendezvous with such a rock, learn more about them, and maybe even learn how to track them better.
  • Dec 1 2011: How would deflecting a comet differ from deflecting an asteroid? Would it be a more challenging problem?
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      Dec 1 2011: Yes, comets are tougher. For one thing, they come from farther away, so on average they're moving faster than asteroid. That gives us less lead time, and it's harder to "catch up" to them using a rocket. Also, when they get near the Sun they start to emit gases and little pieces of rock and ice come off, making the environment around them dangerous for spacecraft. We've gotten up close to them before, several times in fact, so we're learning how to deal with them though!
  • Dec 1 2011: Thanks for the chat Phil, I love the badastronomy blog and your general take on all things universal...Cheers!!!
  • Dec 1 2011: no question for now, just thanks for doing this. I love your blog!
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    Dec 1 2011: What would the minimum size of an asteroid need to be to be life endangering on a mass scale? I heard there was one that passed within the Earth's orbit recently that was around the size of a plane - but surely this isn't big enough to effect life in general? Thanks for your time!
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      Dec 1 2011: Global effects don't come in unless the impactor is pretty big; hundreds of meters across. But even one 30 meters across is big enough to make a crater a kilometer across, which would be bad. Astronomers want to be able to find all the ones bigger than 140 meters across: big enough to do significant damage, but not too small to find easily. Smaller ones are tough to find, bigger ones are easier. it seems like a fair compromise. Eventually, we want to find *all* of them, but for now we need reasonable goals.
  • Dec 1 2011: I'm not sure if this can really be answered...but what about society's reaction to an impending asteroid? A lot of people don't trust science as is, and wouldn't believe we could be saved. I would imagine that a massive education campaign would have to be in place to calm people down.
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      Dec 1 2011: Good point. I think a lot of people would deny the problem, but I would hope enough would take it seriously to force action. I don't know what the reaction would be if we saw something coming and had like two years before impact! I don't know if much could be done outside of just hitting it with a space probe and hoping that's enough to move it out of the way. So the reaction of people here on the Earth with lots of lead time is not something I'm sure i can predict.
  • Dec 1 2011: Not really about asteroids, but what would it take to build a space elevator? Can it be built in our life time and is it really a political decision rather than engineering one? Oh, and is it in danger of asteroids or space debris (do they count as asteroids?)? :D

    Oh yeah, awesome twitter feed! Is it possible to tell what stars will give off GRB? Are there any in the neighborhood?
    • Dec 1 2011: I believe the space elevator relies on the manufacture of a strong carbon ribbon with a particular nano-structure. The longest we have achieved so far is mere inches and we will need thousands of miles worth.
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      Dec 1 2011: We'd need a very unreasonably strong material to make a space elevator, though carbon nanotubes are often talked about this way. My problem with space elevators is protecting them: a single meteor impact on one could destroy it, and then you have BIG problems. The engineering is interesting and maybe possible, and certainly the physics is well understood. But I bet the logistics would prove very difficult.
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    Dec 1 2011: How often does the Sun give off super flares.. and how does this effect the weather here on earth?
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      Dec 1 2011: A recent study indicated that the Sun doesn't produce the kind of superflares you see in movies, but it does sometimes blow off some pretty big events. Look for the "Bastille Day 2003 flare" to see how big these can be! And they can affect us here on Earth, harming satellites, astronauts in orbit, or even causing blackouts here on the ground. I don't think they can affect weather, but they do have those other effects we need to be aware of.
  • Dec 1 2011: Hello Phil,

    Love your work.

    Could you fill us in on what various governments do about monitoring for incoming space debris and if this has been subject to any cuts which may be dangerous due to the necessary funding being lost?
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      Dec 1 2011: Well, NASA does fund telescopes, as does NSF and other agencies. There are lots of telescopes around the world looking, and plans for space-based operations as well. I'd like to see more, of course, but at least there are some things being implemented! Budget cuts are always a problem, and to be honest I'm not sure how that will play out. Hopefully in the long run this is something that will get funded to the extent needed.
      • Dec 1 2011: Thanks. I'm building a live show for Manchester Science Festival for next year which is an immersive experience about Space so I will doubtless be in touch shortly about that. Keep looking up, Andrew
  • Dec 1 2011: Hi Phil, in the video you talked about using a gravity tug to move an incoming asteroid out of a collision course with Earth. Is there an upper limit to the size of asteroid that could be moved using this method?
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      Dec 1 2011: Kinda. :) The bigger the asteroid, the longer it would take to change its velocity. The tug applies a force to the rock, changing its velocity. As Newton figured out, when you apply a force to an object it accelerates, but the more massive it is the lower that acceleration is. So any sized asteroid can be moved using a gravity tug, but the bigger it is the longer lead time we need to move it. In reality, this works best for smaller rocks. Some calculations show we'd only need a few years to move something like Apophis (250 meters across) into a safe path.
  • Dec 1 2011: Thanks Phil for doing this. It was an unexpected surprise and very delightful. Keep up the good work!
  • Dec 1 2011: Hi Phil, wondering if you could expand on mining asteroids as you mentioned in your talk, how this might be done and what kind of materials might be acquired? What asteroids would be best to mine?
  • Dec 1 2011: Interested in the idea of a tug moving an object into orbit. Any chance that it could be tried out on another planet e.g. Mars until we got it right
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      Dec 1 2011: No, Mars is way too big for that! But it would be a great idea to test it on a rock we know is already safe, and measure how much we move it. That way, when one comes along we need to deal with, we're ready.
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    Dec 1 2011: Two part question, first off does the sun have an effect on asteroids in terms of minor pushes in orbit and how can we tell if so and secondly, what about the so called dark asteroids, ones that can't be seen visually, how do we go about detecting them.
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      Dec 1 2011: Actually, yes. If the asteroid spins, the heating of the Sun can act like a very low thrust rocket, called the YORP effect (you can look this up). That's very slow, acting over years,so it's something to keep track of but is not a major problem.

      Dark asteroids are a problem; ones that are so black they are difficult to detect. However, they still glow in the infrared, so we need telescopes that detect IR light (like WISE did) to find those. it's makes things more difficult, but we do have the means to find them!
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    Dec 1 2011: Are there any bets for or against Apophis (striking earth) to be made somewhere?

    Just interested, as the ETA of the rock happens to be on my birthday ;-)
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      Dec 1 2011: Heh. Well, the latest odds of it passing through the keyhole and then hitting us in 2036 are roughly a million to one. I don't know if Vegas is taking bets though. :)
  • Dec 1 2011: If we did decide to make an asteroid moon (I humbly submit the name Moon 2: Electric boogaloo), what sort of horrible tide effects could we expect?
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      Dec 1 2011: Probably nothing to worry about. Even a rock several miles wide would have negligible effect on the Earth.
  • Dec 1 2011: Ah related to my previous question. Obviously a body 2x or more larger than earth would have to be moved MUCH farther away from earth, so as not to affect our orbit, and we wouldn't want it hitting any other planets or worse the Sun.
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      Dec 1 2011: True, but the Earth is 13,000 km across and we know there's nothing out there anywhere near that big; we're talking rocks only a few km across or smaller. So that's not really a concern.
  • Dec 1 2011: Assuming we can develop technology to feasibly predict the path of and accurately redirect asteroids, should we be concerned that a "fine-tuned" method such as the gravity pull might instead be used to redirect an asteroid INTO the keyhole. Ie as a WMD or a threat of a weapon? Should we be worried about Dr. Evil?
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      Dec 1 2011: I do think about that sometimes, but in reality the mission would be a huge team effort, so it would be hard for some nefarious evil mastermind to do that. But it's possible. My bigger worry is, what if some country contributes to the mission, and it's their part that fails, making the asteroid land on their enemy's country? It's pretty far fetched, but just another thing governments have to work out: liability.
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    Dec 1 2011: Assuming 3 years from now on, a really really big asteroid will hit the earth. In the movie, the US government will pay all for the effort to save the earth :). Thanks.

    What do you think in real? Will the financial argue will kill us all?
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      Dec 1 2011: This is a real problem! If it's a global effect, then everyone wants to get involved, and not everyone gets along so well. :) There are groups trying to figure this out, like the B612 Foundation I mention in the talk. I don't know how that will work out. Lots of missions have international cooperation, so the more we do that, the better groundwork we lay to when we really NEED to do it. :)
  • Dec 1 2011: Is there a way for chemists to help out in the field of asteroid deflection? If so, how?
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      Dec 1 2011: That's an interesting questions. We need to understand the composition of asteroids and comets to know how best to deflect them, so chemistry is important. I don't know how to get involved with this field specifically for a chemist, but I know lots of geochemists work for NASA. Poke around the NASA website and see what's there (also Universities which work with NASA).
  • Dec 1 2011: Just for kicks, how difficult would it be to put Apophis in a stable orbit around Earth? I've always wanted another Moon.
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      Dec 1 2011: I actually am not sure. I suspect it could be done with a space tug like I talked about, but it would take far longer than just nudging it into a non-impacting orbit. Still, ion engines have lots of time and if your'e clever - and rocket scientists are - they could use the gravity of the Earth and Moon to help as well. We;ve done that to get probes to other planets, so we know how already!
  • Dec 1 2011: I would like to join a team that analyzes data from night sky to detect NEO's. Do you think there will be programs available similar to Seti@home that would allow us to do just that? Would be nice to have more interaction from the end-user than just computer cpu usage.
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    Dec 1 2011: Another question that comes to mind is the idea of parking an asteroid in orbit, wouldn't something the size and mass of Apophis play with tidal events on the planet?
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      Dec 1 2011: basically, no: it takes a big object to have tidal effects, and even one a few miles across would have a negligible effect. And if it did, we'd make sure it was in a higher orbit. :)
  • Dec 1 2011: I figure that the actual composition of any particular asteroid, eg mass/density in addition to the size/volume would be something to consider as far as the effectiveness of which possible diversion, destruction or other techniques that would be proposed to avoid collision? How would the composition effect choices made about dealing with the possibility of impact...
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      Dec 1 2011: That's true. Some asteroids are fragile, and if you whack them hard enough they might fly apart. That would be bad; then you're dealing with shrapnel. Others are metal and would have no problem absorbing the impact. The bottom line is, we need to know more about asteroids in general so that when we do see one with our number on it, we'll understand how best to deal with it.
      • Dec 1 2011: Exactly... As even with NEO detection abilities increased 10 fold it would seem that given the massive distances involved we would need a fairly long, as in many, many year warning to be able to have any chance of making any difference given current technologies... Not to say that further research in to methods of detection and defense of our planet isn't needed but more to make folks realize that this is an important subject, sort of a cosmic game of pool, lawn bowling or curling that with out some serious thought towards "training" we have a low chance of winning with out committing to further study...
        Maybe instead of spending all the $$$ funding & fighting wars against each other we should focus on the much "bigger picture" eh?
  • Dec 1 2011: The Russians and the Chinese are independently pursuing He-3 lunar mining and fusion. If He-3 can be taken advantage of, the country to do so will be the sole superpower. Why isn't the US? Any other thoughts on He-3 fusion?
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      Dec 1 2011: I have mixed feelings about this. We don't actually *have* an He-3 reactor yet; all these ideas are theoretical on how to make one. So this idea of mining the moon for HE-3 seems a bit premature to me. I'm no expert though. I'd rather we were exploring the Moon for all the other reasons, and then hey, if someone invents He3 fusion reactors, we're already in place to take advantage of them!
  • Dec 1 2011: Is there a possibility to create inexpensive probes that can be spread around the inner solar system to scan for large NEO's, or is that just science fiction?
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      Dec 1 2011: The best way to look for them for now is just using good old telescopes! Some on the ground, some in space; that way we can scan the whole sky and see what's out there. There are so many that it wouldn't work to try to create probes to look for them directly; you just do that once a dangerous one is found.
  • Dec 1 2011: I just saw Melancholia last night. SO it is quite a co-incidence noticing this on facebook today.
    So how would we go about preventing an impact from a body much larger than ours. In the movie they have it moving at 40,000mph. How much lead time would we have detecting a stray planet. At that speed (assuming it was steady) it would be about 3 years/billion miles. Would we be able to detect it 30 years before impact? and would we have any chance of mounting any sort of technologic plan that would move it sufficiently.
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      Dec 1 2011: I haven't' seen the movie yet (I want to!) but the good news is that planets are big and bright, so we've found all the big ones close in to the Sun - and by close in, I mean farther out than Neptune. Even at the speed you mention, something coming in from farther away from that would take decades or centuries to get here. We don't think there are any other big planets beyond Neptune - there might be, but they'd be REALLY far off - so we're OK for the next few millennia at least. :)
  • Dec 1 2011: I've heard that the best option is to launch a vehicle that would impart gravitational force on the approaching asteroid... Would the probe need to be extra massive? Would it need to orbit the asteroid several times in order to change its trajectory significantly? And how fast could a mission be organized, compared to the amount of warning we have?
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      Dec 1 2011: The more massive the impactor, the harder it hits (think American football players). The best thing would be a direct impact trajectory: aim at the rock, and bang! to orbit it you have to slow WAY down, so that makes the impact much less effective.

      As far as how long it would take, I answered that earlier, so it's on this Q&A somewhere; scroll down to see it!
  • Dec 1 2011: Hi Phil,
    What is the time of detection before impact nowadays?
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      Dec 1 2011: Well, that depends on what you mean. A big rock, capable of doing global or regional damage, might be seen years in advance. Something small, like 100 meters in size, might not be seen literally until we see the flash in the sky. We have seen small rocks before they hit us, like 2008 TC3, which was 2 meters across and seen a day before it broke up over Africa. Even a day's warning might be helpful for a bigger rock, but the longer the lead time, the better.
  • Dec 1 2011: I've probably watched too many Bruce Willis movies, but would fracturing the asteroid do anything helpful?
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      Dec 1 2011: Yes and no. If it's done way way way in advance it can help. What you don't want are lots of little piece headed toward us! But it you do break it up years in advance, then you have that many more pieces to keep track of which might hit us later. Best to keep it in one piece and move it all at once to a safe orbit.
  • Dec 1 2011: What other applications could there be for the ion drive besides pulling an asteroid out of the way? For example, could it ever be a viable option for space travel?
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      Dec 1 2011: Yes! In fact, ion drives have been used twice in spacecraft successfully, including the current Dawn mission which is orbiting the asteroid Vesta. Ion drives are very efficient. Even though they accelerate a rocket very slowly, they do so over long periods of time, and can actually get a probe moving *faster* than a chemical rocket can, if you don't mind waiting longer.
  • Dec 1 2011: Hello Phil. Big fan of your blog and outreach.
    I have a question about the Levy-Shoemaker asteroid that struck Jupiter. Is there enough information about the trajectory of that asteroid to project it's path and see if it would have been a danger to Earth?
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      Dec 1 2011: I think SL9 was in orbit around Jupiter, so there was never a danger of it hitting us. But it was just one of thousands of random comets out there! So we need to keep our eyes open to watch for any others. We get passed by comets all the time, and they are very, very rarely a danger to us. Still, the point it to be aware of them.
  • Dec 1 2011: The interface confuses me: "This conversation will close in 52 minutes, on December 1, 2011 at 11:00:00 AM" and "This Conversation will open on December 1st, 1 pm EST". No links to listen/join. Perhaps I'm just not TED material? :-(
  • Dec 1 2011: There are a limited number of opportunities to nudge asteroids, based on their orbits. Re the asteroid slated to come near Earth in 2016 (?) when is the soonest we could apply the "nudge" so as to make it miss the keyhole. And how soon after the nudge would we know we were successful?
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      Dec 1 2011: Apophis will pass us in 2029, and if it passes at just the right distance will hit us in 2039 ( though the odds of that are VERY low). If we nudge it before it passe us, we only have to move it a little bit, because then Earth;'s gravity will warp it into a safe orbit for us, doing all the work. If we wait until *after* it passes, it's much harder, because then the tug has to do all the work.

      Plus, the distance we have to move it before 2029 is small, only a few hundred yards. It only has to miss the keyhole, which is small. But if it does pass through the keyhole, we have to move it thousands of kilometers, because then it has to miss the whole Earth, which is a much bigger target.

      But remember, the odds of it hitting us at all are like a million to one. :)
  • Dec 1 2011: Are we devoting enough resources to the hunt for Near Earth Objects?
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      Dec 1 2011: The answer to that will almost always be "no", but that's because we can always do more! We do have a lot of telescopes looking, and more are planned. But it's a big sky, and we could always use more eyes on it.
      • Dec 1 2011: How can backyard/hobby astronomers get involved?
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    Dec 1 2011: I keep on hearing about different ways to move asteroids. I was wondering if one could attach a tow line to where the spin is the least, with a rotating coupler arm, so it could continue to spin and then with a few powerful rockets attached to a lot of mass, drag the asteroid as needed.
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      Dec 1 2011: I've thought of that myself! But I think in reality that's pretty hard, and with so many moving parts it has a bigger chance of failing than, say, slamming the asteroid with a small spacecraft to knock it into a safe path, and then nudging it with a gravity tug. Plus, I'm not sure we could make a cable strong enough to do the trick! It would have to be hundreds if not thousands of meters long. That's a big task!
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        Dec 1 2011: I'd think a carbon nanotube composite fiber cable should have the strength and would be extremely light even at the length of the cable. Plus it would require very few moving parts, a firing mechanism with a backup to fire the line with enough force to embed a holding claw at the end of the line and then a rocket. To be safe, one could send a pair just in case. You'd still have the same spacecraft, but it'd be driving instead of crashing. Also with a setup like that, I'd think you could then correct for excess drift of the meteoroid, where as by slamming into it, you may push it too much.
  • Dec 1 2011: Hi Phil!

    In your TED talk you mentioned gently pushing asteroids out of our way using a probe with ion drives. What about other methods? With a strong enough laser, could you nudge an asteroid just right to move it to a safer trajectory?

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      Dec 1 2011: Yes, there are other ideas. The laser one might work: you heat up the surface of the rock, which turns into rapidly expanding gas, pushing on the asteroid. That acts like a rocket, and you can nudge the asteroid onto a safe path. But that takes ridiculous amounts of energy, and it's not clear how you'd power such a laser... or if we have one that powerful.

      You could also use a giant mirror to focus sunlight on it, but again there are engineering difficulties with that; getting something that big to an asteroid has never been done, though there have been some smaller-scale experiments like that performed in Earth orbit (unfolding a large object, and so on).

      So we have options! We just need to work on them.